Highly Active and Selective Catalysts for the Formation of α-Aryl Ketones

Abstract

Bulky, electron-rich phosphine ligands with a biphenyl backbone, when combined with Pd(OAc)2, give highly active catalysts for the α-arylation of ketones. The ligand 2-methyl-2‘-dicyclohexylphosphinobiphenyl is particularly effective, and with 0.1−1.0 mol % Pd, a large variety of aryl halides and ketones react efficiently and with high selectivity. For two types of substrates, the ligands BINAP and Xantphos are more effective than the biphenyl-based ligands. It is also shown that K3PO4 can be used as the base in these reactions, and that base-sensitive functional groups are better tolerated if this is used instead of NaO t Bu or NaHMDS. In some cases, α-aryl ketones can be produced without adding a ligand to the reaction. Although the substrate scope of the ligandless conditions is limited, some combinations react in high yield, and in one case, 100 000 turnovers were obtained. The results of experiments on the Pd-catalyzed arylation of diethyl malonate, cyclic 1,3-diketones, and nitroalkanes are also reported.

A New Series of Estrogen Receptor Modulators: Effect of Alkyl Substituents on Receptor-Binding Affinity

“…Compound 37 38) was subjected to intramolecular Friedel-Crafts acylation to give 38. Application of Buchwald's arylation 39) permitted the smooth conversion of 38 to 39. CeCl 3 -promoted demethylation, NaBH 4 -reduction and acid-promoted dehydration produced 41.…”

Biaryl Phosphane Ligands in Palladium‐Catalyzed Amination

“…[2] These phosphines have been used as ligands for gold, [3][4][5][6][7][8][9][10][11] silver, [12] rhodium, [13,14] ruthenium [15][16][17] and copper [18] where they have been shown to impart improvements in reactivity and catalyst stability. It is in reactions catalyzed by palladium, however, that they have had by far the greatest impact including the Sonogashira, [19] Negishi, [20] Hiyama, [21][22][23] Kumada [24] and Suzuki [25][26][27][28][29][30] cross-coupling reactions, Heck reaction, [31][32][33] enolate arylation [34][35][36][37] and allylation, [38] reductive cyclization [39] and etherification, [40][41][42][43] silylation, [44] borylation, [45][46][47] cyanation, [48,…”

A new entry to o,o’-dihalogenated deoxybenzoins by palladium-catalyzed α-arylation of 2'-chloroacetophenones

“…Another remarkable feature was that the conditions optimized for the isolation of 2-bromoaryl intermediates depicted in Scheme 1 ( Table 1, entries 1-2) 6,7 provided complex mixtures in this case, and it was necessary to increase the temperature and the amount of base to detect the target ethanone 3a ( Table 1, entries 3-4), though with relatively low yields (46%) and the occurrence of several side-products which made the purification task difficult. Then, a variety of procedures and variations based on previous work of the group of Hartwig, 9 Buchwald, 10 In most of the performed assays, the reaction mixture turned red after 0.5 h of reaction. The structures 6-8 depicted below were tentatively proposed as possible complexes that would explain such coloration 12 and also to some extent the hindrance to reach target ethanone 3.…”